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Evaluation of analgesic and anti-inflammatory activities of Hydrocotyle umbellata L., Araliaceae (acariçoba) in mice

Abstracts

The Hydrocotyle umbellata L. is a specimen of the Araliaceae family popularly known as acariçoba. Its indications in folk medicine include treatment of skin ulcers, and rheumatism. The aim of this study was to evaluate the antinociceptive and anti-inflammatory activities of the ethanolic extract from acariçoba's underground parts (EEA). EEA reduced the nociceptive response of the animals as evaluated in the acetic acid-induced writhing test and in both phases of formalin test. EEA also presented a supraspinal analgesic activity by increasing the pain latency in the hot plate test. Moreover, EEA reduced the leukocytes migration and plasma extravasation to pleural cavity in the carrageenan-induced pleurisy, besides reducing the edema induced by carrageenan until the second hour and also the edema induced by dextran. In conclusion our results showed that EEA of H. umbellata L. presents analgesic and anti-inflammatory activities, and that a blockade of activity or reduction in the release of different mediators, such as histamine and serotonin, could be involved in these pharmacologic effects.

Acariçoba; anti-inflammatory; antinociceptive; Biomedical Sciences; Hydrocotyle umbellata L


A Hydrocotyle umbellata L., é uma espécie pertence à família Araliaceae, popularmente conhecida como acariçoba. Suas indicações na medicina popular incluem tratamento de úlceras cutâneas, eczemas e reumatismo. O objetivo deste trabalho é avaliar as atividades antinociceptiva e/ou anti-inflamatória do extrato etanólico das partes subterrâneas da acariçoba (EEA). O EEA reduziu a resposta nociceptiva do animais no teste das contorções abdominais induzidas por ácido acético e em ambas as fases do teste da formalina. O EEA também mostrou uma atividade analgésica supra-espinhal ao aumentar o limiar nociceptivo no método da placa quente. O EEA reduziu tanto o número de leucócitos migrados quanto o extravasamento plasmático para a cavidade pleural na pleurisia induzida por carragenina. Além de reduzir o edema de pata induzido por carragenina até a segunda hora e também o edema de pata induzido por dextrana. Em conclusão os nossos resultados mostram que o EEA de H. umbellata L. possui atividades analgésica e anti-inflamatória, e que um bloqueio da atividade ou redução da liberação de diferentes mediadores tais como histamina e serotonina, podem estar envolvidos nestes efeitos farmacológicos.

Acariçoba; anti-inflamatório; antinociceptivo; Ciências Biomédicas; Hydrocotyle umbellata L


INTRODUCTION

The Hydrocotyle umbellata L., popularly known as acariçoba, is a creeping specimen that belongs to the Araliaceae family. It species is native in Argentina, Cuba, India and Brazil, where this plant can be found in MidSouth states of São Paulo, Paraná, Santa Catarina, Rio Grande do Sul and Goiás (Corrêa 1984, Fischer et al. 1994Fischer DCH, Kato ETM and Oliveira F. 1994. Estudo farmacognóstico de Hydrocotyle bonariensis Lam., Adulterante de Centella asiática (L.) Urban. LECTA Rev Farm Biol 12(2): 71-102.).

Plant species as Hydrocotyle umbellata L. and Hydrocotyle asiatica (L.) have great interest in folk phytotherapy and in the Ayurvedic medicine (Indian) because of its potential anxiolytic, memory stimulant effects and its use in the cosmetic industry (Reis et al. 1992Reis HHT, Gomes LM, Freitas MRF, Nogueira JCM, Silva E, Maranhão MF and Carneiro DM. 1992. Como utilizar plantas medicinais. Goiânia: Sistema Único de Saúde- Ministério da Saúde, 74 p.). Ethnobotanical studies suggest that these plants are used as true panaceas, being employed as healing, diuretic, anti-hypertensive and to treat skin ulcers, eczema, dermatitis, psoriasis, erysipelas, rheumatism, tuberculosis, and spleen, liver and intestinal disorders. H. umbellata L. leaves in high doses produce emetic effects and are potentially toxic (Corrêa 1984, Reis et al. 1992Reis HHT, Gomes LM, Freitas MRF, Nogueira JCM, Silva E, Maranhão MF and Carneiro DM. 1992. Como utilizar plantas medicinais. Goiânia: Sistema Único de Saúde- Ministério da Saúde, 74 p., Fischer et al. 1994Fischer DCH, Kato ETM and Oliveira F. 1994. Estudo farmacognóstico de Hydrocotyle bonariensis Lam., Adulterante de Centella asiática (L.) Urban. LECTA Rev Farm Biol 12(2): 71-102.). Our previous study found that the ethanolic extract from H. umbellata L. showed anxiolytic-like and sedative effects in mice (Rocha et al. 2011Rocha FF, Almeida CS, Santos RT, Santana SA, Costa EA, Paula JR and Vanderlinde FA. 2011. Anxiolytic and sedative effects of Hydrocotyle umbellata L., Araliaceae, extract in mice. Rev Bras Farmacogn 21: 115-120.).

Acariçoba is a plant with long and petiolate leaves, white small and numerous flowers and a small fruit-shaped capsule flattened. In the Brazilian folk medicine a decoction of its leaves (fresh or dried) is used as baths, and orally for the treatment of inflammatory processes (Pharmacopeia dos Estados Unidos do Brasil, 1926 – Brazilian Pharmacopeia). Inflammation is the body's immediate response the tissue aggressions caused by pathogens, toxic substances or physical harm. The inflammatory process is characterized by the release of several mediators and the development of the classic signs of inflammation such as swelling, warmth, redness and pain (Queiroz et al. 2010).

Phytochemical studies showed the presence of flavonoids, essential oils, saponins, tannins and absence of alkaloids and anthracene derivatives (Adams et al. 1989Adams AA, Norris JA and Aabry TJA. 1989. Flavonoids from Hydrocotyle umbellata L. (Umbelliferae). Latino Amer Quim 20: 67-68., Fischer et al. 1994Fischer DCH, Kato ETM and Oliveira F. 1994. Estudo farmacognóstico de Hydrocotyle bonariensis Lam., Adulterante de Centella asiática (L.) Urban. LECTA Rev Farm Biol 12(2): 71-102.). Thus, the aim of this study was to evaluate the pharmacological activity of ethanolic extract from Hydrocotyle umbellata L. (acariçoba) underground parts in pain and inflammation models seeking to scientifically give support the use of this plant by the Brazilian population.

MATERIALS AND METHODS

Botanical Material and Extraction

Hydrocotyle umbellata L. underground parts were authenticated by Prof. Heleno Dias Ferreira (Institute of Biological Sciences/Federal University of Goiás/ICB/UFG) and collected in the Medicinal Plants Garden of Faculty of Pharmacy from the Universidade Federal de Goiás (UFG). A voucher specimen has been deposited in the Herbarium of UFG under the number UFG/22.394.

To prepare the ethanolic extract from acariçoba underground parts (EEA) the vegetal material was dried and milled and the powder was then macerated in ethanol (96° GL) for three days, followed by filtration. After that, the filtrated was concentrated to dryness under reduced pressure in rotavapor (at 40 °C). The extract was obtained by this extractive process with a yield of 3.0 %.

Animals

Male Swiss albino mice weighing approximately 30 g from the Central Animal House of UFG were used in this study. The animals received food and water ad libitum and were maintained in a room with light and temperature regulation. All experimental protocol was developed in accordance with the principles of ethics and animal welfare designated by the SBCAL/COBEA, as well as approved by the Ethics Committee in Research of UFG (number 104/08).

Drugs

Acetone (Isofar, Brazil); carrageenan (Sigma, USA); cyproheptadine (Sigma, USA); crotonoil (Sigma, USA); dexamethasone - decadron (Ache, Brazil); dextran (Sigma, USA); ethanol 95% P.A. (Synth, Brazil); formaldehyde (Synth, Brazil); glacial acetic acid (Vetec, Brazil); Heparin (Hipolabor, Brazil); indomethacin (Prodome, Brazil); morphine - Dimorf® (Cristalia, Brazil); NaCl (Belga); Türk solution (Bioshop, Brazil).

Acute Oral Toxicity Study

Acute oral toxicity assay was performed in adult male albino Swiss mice (30-35 g) divided into different groups following the OECD guidelines-423 (OECD, 2001). Two groups of mice n=3 albino Swiss were treated with EEA (4,000 mg/kg), orally. The vehicle group received distilled water at the same volume and route.

Analgesic Activity

The analgesic activity of the ethanolic extract from underground parts acariçoba was investigated using the following models.

Acetic acid-induced abdominal writhing

Experimental groups of mice (n = 9) were treated (p.o.) with vehicle (10 mL/kg), EEA (250, 500 or 1,000 mg/kg) or indomethacin (10 mg/kg) 60 min before the administration of 1.2% acetic acid solution (10 mL/kg, i.p.). The number of writhing produced in each group for the following 30 min was counted and the results were expressed as mean ± standard error of mean (SEM) in percentage of control group (Koster et al. 1959Koster R, Anderson M and De Beer EJ. 1959. Acetic acid for analgesic screening. Fed Proc 18: 412-416., Vacher et al. 1964Vacher PJ, Duchene-Marullaz PE and Barbot P. 1964. A propos de quelques produits usuels – comparaisonm de deux méthodes d'étude des analgésiques. Med Exp 11: 51-58.).

Formalin-induced pain

Experimental groups of mice (n = 9) were treated with vehicle (10 mL/kg, p.o.), EEA (1,000 mg/kg, p.o.), indomethacin (10 mg/kg, p.o.) or morphine (5 mg/kg s.c.), 60 min after the p.o. treatments or 30 min after s.c. treatment. The animals were treated with formalin 3% (20 µL) in the right hindpaw. Following injection of the phlogistic agent, the mouse was placed into an acrylic box, with a mirror placed under the box at 45° to facilitate the observation of the formalin-injected paw for 30 min. The pain reaction time (time for licking the paw) was observed in two periods, 0-5 min (neurogenic pain) and 15-30 min (inflammatory pain) (Hunskaar and Hole 1987Hunskaar S and Hole K. 1987. The formalin test in mice: dissociation between inflammatory and non-inflammatory pain. Pain 30: 103-114.).

Hot plate test

The latency (in seconds) to reaction of the mice, expressed as licking, shaking or lifting the hind paws, on hot plate at 55.5 + 0.5°C was analyzed according to Woolfe and MacDonald (1944)Woolfe G and MacDonald AD. 1944. The evaluation of the analgesic action of pethidine hydrochloride. J Pharmacol Exp Ther 80: 300-307.. The animals were divided into five experimental groups (n = 9) consisting of animals treated with vehicle (10 mL/kg, p.o.), EEA (250, 500, or 1,000 mg/kg, p.o.) or morphine (10 mg/kg, s.c.). The latency to pain reaction was measured at -60, -30, 0, 30, 60, 90 and 120 min of the treatment.

Anti-Inflammatory Activity

The anti-inflammatory activity of the ethanolic extract from acariçoba underground parts was investigated using the following models.

Carrageenan-induced pleurisy

Each animal received, intravenously, 200 µL of 2.5% Evan's blue in normal saline, two hours after the animals were being treated with vehicle (10 mL/kg, p.o.), EEA (250, 500, or 1,000 mg/kg, p.o.) or dexamethasone (2 mg/kg, p.o.). One hour after the treatments, the animals received an injection of 100 µL of 1% carrageenan into pleural cavity. Four hours after phlogistic agent administration the pleural exudate was collected with 1 mL of heparinized PBS. One aliquot was used to count the number of total leukocytes, using Türk solution, in a Neubauer's chamber. Other aliquot was used to determine the Evan's blue concentration on a spectrophotometer at 600 nm (Saleh et al. 1999Saleh TSF, Calixto JB and Medeiros YS. 1999. Effects of anti-inflammatory drugs upon nitrate and myeloperoxidase levels in the mouse pleurisy induced by carrageenan. Peptides 20(8): 949-956., Vinegar et al. 1973Vinegar R, Truax JF and Selph JL. 1973. Some quantitative temporal characteristics of carrageenan-induced pleurisy in the rat. Proc Soc Exp Biol Med 14: 711-714.).

Croton oil-induced ear edema

Animals were treated (p.o.) with vehicle (10 mL/kg, p.o.), dexamethasone (2 mg/kg, p.o.), or EEA (250, 500, or 1,000 mg/kg, p.o.). One hour after the treatments, the inflammation was induced by the application of 2.5 % (v/v) croton oil solution in acetone (2.5%) on the inner surface of the right ears. The same volume of acetone was applied to the left ear (Zanini et al. 1992Zanini JCJR, Medeiros YS, Cruz AB, Yunes RRA and Calixto JB. 1992. Action of compounds from Mandevilla velutina on croton oil-induced ear oedema in Mice. A comparative study with steroidal and nonsteroidal antiinflammatory Drugs. Phytother Res 6(1): 1-5.). After 4 hours, the mice were sacrificed and segments of both ears were removed. The inflammatory was measured by the difference between the weights of the segments.

Carrageenan-induced paw edema

Groups of mice (n =9) were treated orally with vehicle (10 mL/kg), EEA (250, 500 or 1,000 mg/kg) or indomethacin (10 mg/kg) 1 h before the injection of 50 µL of 1% carrageenan in the right paw. The left paw was used as control and received the same volume of 0.9% NaCl solution. Then, the edema was measured by the difference in the volume between the paws using a plethysmometer (Ugo Basile Co. - Italy) at several time-points after injection of phlogistc agent (Passos 2007Passos GF. 2007. Anti-inflammatory and anti-allergic properties of the essential oil and active compounds from Cordia verbenacea. J Ethol 110: 323-333.).

Dextran-induced paw edema

Experimental groups of mice were treated orally with vehicle (10 mL/kg), EEA (1,000 mg/kg) or cyproheptadine (5 mg/kg) one hour before the injection of 50 µL of 1% dextran in the right paw. The left paw was used as control and received the same volume of 0.9% NaCl solution. After the injections the edema was measured in time intervals of 0, 30, 60, 90 and 120 min using a plethysmometer (Ugo Basile Co.- Italy). The formation of edema was assessed by the difference between the paws volume.

Statistical Analysis

Results were expressed as means ± S.E.M. Differences between two means were detected using the Student's t test. Differences between more than 2 means were detected using one-way analysis of variance (ANOVA) followed by Student-Newman-Keuls' test. The results were considered significant when p < 0.05 (Sokal and Rohlf 1981Sokal RR and Rohlf FJ. 1981. Biometry: the Principles and Practice of Statistics in Biological Research, New York, 859 p.).

RESULTS

Acute Oral Toxicity

In the acute oral toxicity test doses up to 4,000 mg/kg of EEA did not cause any death in mice during 14-days of observation. Mice did not show any signs of toxicity or change in general behavior or other physiological activities.

Acetic Acid-Induced Abdominal Writhing

The EEA (250, 500 or 1,000 mg/kg) produced a significant reduction (24, 32 and 41%, respectively) in the number of acetic acid-induced writhes when compared with control values (vehicle 10 mL/kg; 113.0 ± 6.4). The indomethacin reduced the abdominal writhes by 40% (Figure 1).

Figure 1
Effect of the ethanolic extract from acariçoba underground parts (EEA) (250, 500 and 1,000 mg/kg p.o.) in the number of acetic acid-induced writhes in mice. Indomethacin (10 mg/kg p.o.) was used as positive control. Vertical bars represent mean ± SEM of cumulated writhings in 30 min for each experimental group. *p < 0.05; ***p < 0.001. According ANOVA followed by Student-Newman-Keuls' test.

Formalin-Induced Pain

Treatment with EEA 1,000 mg/kg p.o. or morphine 10 mg/kg s.c. reduced by 41 and 99%, respectively, the licking time of hind paw after the intraplantar injection of formalin in the neurogenic phase (0-5 min) from control values (vehicle 10 mL/kg; 62.6 ± 4.8 s). In the inflammatory phase (15-30 min), treatment with EEA 1,000 mg/kg p.o., morphine or indomethacin reduced the licking time by 48, 99 and 43% respectively, from a control value of 131.0 ± 17.1 s (Figure 2).

Figure 2
Effect of the ethanolic extract from acariçoba underground parts (EEA) (1,000 mg/kg p.o.), indomethacin (10 mg/kg p.o.) and morphine (10 mg/kg s.c.) on the licking time of Formalin-induced pain, in mice, in the first phase (0-5 min) and the second phase (15-30 min). Vertical bars represent mean ± SEM of reaction time pain, in seconds. *** p < 0.001 vs first phase control; ## p < 0.01 and ### p < 0.001 vs second phase control. According ANOVA followed by Student-Newman-Keuls' test.

Hot Plate Test

Treatment with EEA increased by 60% the latency to reaction only with the highest dose (1,000 mg/kg) 1 h after the treatment from a control value (vehicle 10 mL/kg) of 10.6 ± 0.82. The positive control morphine (10 mg/kg s.c.) increased the latency to reaction to 90 min after the treatment (Figure 3).

Figure 3
Effect of the ethanolic extract from acariçoba underground parts (EEA) (250, 500 and 1,000 mg/kg p.o.) or morphine (10 mg/kg s.c.) on the nociceptive response of mice in the hot-plate test. Values are expressed as mean ± SEM of the latency for the nociceptive behavior. * p < 0.05; *** p < 0.001. According ANOVA followed by Student-Newman-Keuls' test.

Carrageenan- Induced Pleurisy

The EEA (500 and 1,000 mg/kg) or dexamethasone (2.0 mg/kg) reduced by 40, 44 and 50 % the number of migrated leukocytes/ mL to the pleural cavity from a control value of 4.8 ± 0.46 × 106 leukocytes/ mL (vehicle 10 mL/kg), respectively (Figure 4). Treatment with EEA (250, 500 and 1,000 mg/kg) reduced by 33, 38.8 and 50% the Evan's blue concentration in the pleural exudate from a control value (vehicle 10 mL/kg) by 1.8 ± 0.17 µg/mL, respectively. Dexamethasone reduced this value by 50% (Figure 5).

Figure 4
Effect of the ethanolic extract from acariçoba underground parts (EEA) (250, 500 and 1,000 mg/kg p.o.), in carrageenan-induced pleurisy in mice. Dexamethasone (2.0 mg/kg p.o.) was used as positive control. The bars represent the means ± SEM of number of migrated leukocytes /mL (× 106) migrated to pleural cavity after carrageenan injection relative to control group. *** p < 0.001. According ANOVA followed by Student-Newman-Keuls' test.

Figure 5
Effect of the ethanolic extract from acariçoba underground parts (EEA) (250, 500 and 1,000 mg/kg p.o.), in carrageenan-induced pleurisy in mice. Dexamethasone (2.0 mg/kg p.o.) was used as positive control. The bars represent the means ± SEM of Evan's blue concentration (µg/mL) in the pleural exudate after carrageenan injection. ** p < 0.01 and *** p < 0.001. According ANOVA followed by Student-Newman-Keuls' test.

Croton Oil-Induced Ear Edema

EEA (250, 500 and 1,000 mg/kg) reduced the edema by 20, 25 and 38%, in a dose-dependent manner, from a control value (vehicle 10 mL/kg) of 17.8 ± 0.77 mg, respectively. Dexamethasone (2.0 mg/kg) reduced the edema by 78% (Figure 6).

Figure 6
Effect of the ethanolic extract from acariçoba underground parts (EEA) (250, 500 and 1,000 mg/kg p.o.), in croton oil-induced ear edema in mice. Dexamethasone (2.0 mg/kg p.o.) was used as positive control. Vertical bars represent mean ± SEM of the difference between left and right ear plugs, in milligrams. * p < 0.05; ** p < 0.01; *** p < 0.001. According ANOVA followed by Student-Newman-Keuls' test.

Carrageenan-Induced Paw Edema

In this model, treatment with EEA (250, 500 and 1,000 mg/kg) or indomethacin reduced the edema (µL) at the first and second hour. At the first hour, it was observed a reduction of 27, 44, 57 and 21% from control value (vehicle 10 mL/kg) of 55.0 ± 4.3, respectively. At the second hour, from control value of 57.66 ± 3.51 to 39.33 ± 2.54; EEA reduced the edema by 32, 59 and 47%, respectively. The indomethacin reduced the edema by 45%. After the second hour of edema, only indomethacin was able to reduce the edema formation (Figure 7).

Figure 7
Effect of the ethanolic extract from acariçoba underground parts (EEA) (250, 500 and 1,000 mg/kg p.o.) or indomethacin (10 mg/kg p.o.) on the carrageenan-induced paw edema. The edema was measured 1, 2, 3 and 4 h after the injection of the phogistic agent. Vertical bars represent mean ± SEM of the difference between the volumes of the paws. *p < 0.05; **p < 0.01; ***p < 0.001. According ANOVA followed by Student-Newman-Keuls' test.

Dextran-Induced Paw Edema

In the model of dextran-induced paw edema, treatment with EEA (1,000 mg/kg) or cyproheptadine (5.0 mg/kg) reduced the edema (µL) of 36 and 37%, respectively, at 30 min after the injection of dextran, from a control value (vehicle 10 mL/kg) of 87.8 ± 7.4, as well as, at 60 min after the treatment, there was a reduction of 41 and 45%, from control value (60.0 ± 7.3), respectively (Figure 8).

Figure 8
Effect of the ethanolic extract from acariçoba underground parts (EEA) (1,000 g/kg p.o.) or cyproheptadine (5.0 mg/kg p.o.) on the dextran-induced paw edema. The edema was measured 0, 30, 60, 90 and 120 min after the injection of dextran. Vertical bars represent mean ± SEM of the difference between the volumes of the paws. * p < 0.05 and ** p < 0.01. According ANOVA followed by Student-Newman-Keuls' test.

DISCUSSION

In the present study the analgesic and anti-inflammatory effects of the ethanolic extract (EEA) from acariçoba's underground parts was evaluated, since this plant has the popular reputation of these effects. The results obtained with this extract in the acute oral toxicity evaluation indicated no toxic effects (Santana 2001Santana SA. 2001. Tese de mestrado, Estudo Farmacognóstico da Acariçoba, Hydrocotyle umbellata L. Araliaceae 4, 65 p. (Unpublished).).

The acetic acid induce nociception by stimulates nociceptive fibers directly, besides promote the release of endogenous mediators involved in pain modulation, among which is bradykinin, serotonin, histamine and prostaglandins (Whittle 1964Whittle BA. 1964. Release of a kinin by intraperitoneal injection of chemical agents in mice. Int J Neuropharmacol 3: 369-378., Berkenkopf and Weichman 1988Berkenkopf JW and Weichman BM. 1988. Production of prostacyclin in mice following intraperitoneal injection of acetic acid, phenylbenzoquinone and zymosan: its role in the writhing response. Prostaglandins 36(5): 693-709., Chau 1989Chau TT. 1989. Analgesic testing in animals models. In: Pharmacological models in the control of inflammation. Alan R. Liss Inc., p. 195-212.). Treatment with EEA decreased the number of acetic acid-induced writhing. However, this test is considered as having high sensitivity but low selectivity, thus false-positive results may occur with different groups of drugs such as antihistaminics, central nervous system stimulants, monoamine oxidase inhibitors (MAOIs), serotonin antagonists, muscle relaxants and neuroleptics (Ikeda et al. 2001Ikeda Y, Ueno A, Naraba H and OH-Ishi S. 2001. Involvement of vaniloid receptor VR1 and prostanoids in the acid-induced writhing responses of mice. Life Sci 69: 2911-2919., Le Bars et al. 2001).

The formalin test, on the other hand, allows the study of two types of pain. The first phase (0-5 min) corresponds to a neurogenic pain with the involvement of mediators such as substance P, bradykinin, histamine and serotonin, and the evidence of direct stimulation of nociceptors by formalin (Dubuisson and Dennis 1977Dubuisson D and Dennis SG. 1977. The formalin test: a quantitative study of the analgesic effects of morphine, meperidine, and brain stem stimulation in rats and cats. Pain 4(2): 161-174., Hunskaar and Hole 1987Hunskaar S and Hole K. 1987. The formalin test in mice: dissociation between inflammatory and non-inflammatory pain. Pain 30: 103-114., Shibata et al. 1989Shibata M, Ohkubo T, Takahashi H and Inoki R. 1989. Modified formalin test: characteristic biphasic pain response. Pain 38: 347-352., Corrêa and Calixto 1993Corrêa CR and Calixto JB. 1993. Evidence for participation of B1 and B2 kinin receptors in formalin-induced nociceptive response in mouse. Br J Pham 110: 193-198., Munron 2007Munron G. 2007. Dopamine D1 and D2 recptor agonism enhances antinociception in mediated by the serotonin and noradrenaline reuptake inhibitor duloxetine the rat formalin test. Eur J Ethol 575: 66-74.). The second phase (15-30 min) is associated with the production and release of various pro-inflammatory mediators such as histamine, bradykinin, serotonin, prostaglandins, tachykinins and glutamate by cells activated by formalin (Fujimaki et al. 1992Fujimaki H, Kawagoe A, Bissonnette E and Befus D. 1992. Mast cell response to formaldehyde. 1. Modulation of mediator release. Int Arch Allergy Immunol 98(4): 324-331., Santos and Calixto 1997Santos AR and Calixto JB. 1997. Further evidence for the involvement of tachykinin receptor subtypes in formalin and capsaicin models of pain in mice. Neuropeptides 31: 381-389., Cao et al. 1998Cao YQ, Mantyh PW, Carlson EJ, Gillespie AM, Epstein CJ and Basbaum AI. 1998. Primary afferent tachykinins are required to experience moderate to intense pain. Nature 6674(4): 390-392., Omote et al. 1998Omote K, Kawamata T, Kawamata M and Namiki A. 1998. Formalin-induced release of excitatory amino acids in the skin of the rat hindpaw. Brain Res 787(1): 161-164. and Beirith et al. 2002Beirith A, Santos AR and Calixto JB. 2002. Mechanisms underlying the nociception and paw oedema caused by injection of glutamate into the mouse paw. Brain Res 924 (2): 219-228.). The formalin also activates primary afferent sensory neurons through a specific and direct action on TRPA1, which is a member of the Transient Receptor Potential family of cation channels that is highly expressed by a subset of C-fiber nociceptores (McNamara et al. 2007McNamara CR, Mandel-Brehm J, Bautista DM, Siemens J, Deranian KL, Zhao M, Hayward NJ, Chong JA, Julius D, Moran MM and Fanger CM. 2007. TRPA1 mediates formalin-induced pain. Proc Natl Acad Sci 104(33): 13525-13530.).

Considering the fact that formalin-induced pain test is more specific for pain study than abdominal contortions induced by acetic acid, with the expectation to confirm the true analgesic activity of this EEA, we decided to work with the higher dose.

The EEA reduced the pain reactivity in both phases of the formalin test. This effect may be a TRPA1 inhibition, seen that TRPA1 antagonist receptor eliminated pain-related flinching in both phases of the formalin response in vivo (McNamara et al. 2007McNamara CR, Mandel-Brehm J, Bautista DM, Siemens J, Deranian KL, Zhao M, Hayward NJ, Chong JA, Julius D, Moran MM and Fanger CM. 2007. TRPA1 mediates formalin-induced pain. Proc Natl Acad Sci 104(33): 13525-13530.). But also, this action in the both phases of formalin test does not allow us to separate an anti-inflammatory activity independent of a central analgesic, making necessary to evaluate the extract in specific models of inflammation. The inflammation is a complex process, thus it is necessary to use various inflammation models, involving the analysis of several parameters, to evaluate an anti-inflammatory activity of a given substance (Chiabrando et al. 1989Chiabrando C, Castelli MG, Cozzi E, Fanelli R, Campoleoni A, Balotta C, Latini R and Garattini S. 1989. Antiinflammatory action of salicylates: aspirin is not a prodrug for salicylate against rat carrageenin pleurisy. Eur J Phycol 159: 257-264.).

The highest dose of EEA also increased the nociceptive threshold to thermal stimulation 1 h after the treatment. This effect in the hot plate test suggests a central analgesic activity (Yaksh and Rudy 1977Yaksh TL and Rudy TA. 1977. Studies on direct spinal action of narcotics in production of analgesia in rat. J Pharmacol Exp Ther 202: 411-28.).

In the carrageenan-induced pleurisy test, it is possible to evaluate an important inflammation parameter, the leukocyte migration. Carrageenan is a phlogistic agent that when injected in the pleural cavity promotes a severe inflammation, in which various inflammatory mediators are released, such as histamine, serotonin, cytokines and eicosanoids, resulting in an intense leukocyte migration, and an pleural exudate formation caused by protein extravasation, being this extravasation indirectly quantified by Evan's blue concentration in the pleural exudate (Steele and Wilhelm 1966Steele RH and Wilhelm DL. 1966. The inflammatory reaction in chemical injury 1. Increased vascular permeability and erythema induced by various chemicals. J Exp Pathol 47: 612-623.).

Treatment with EEA at the doses of 500 and 1,000 mg/kg reduced the number of leukocytes migration into the pleural cavity. These effects suggest a reduction in the level of mediators responsible for the cell migration, such as cytokines (IL-1 and TNF-α), nitric oxide, prostanoids, serotonin and histamine (Henriques et al. 1987Henriques MG, Silva PM, Martins MA, Flores CA, Cunha FQ, Assurey-Filho J and Cordeiro RS. 1987. Mouse paw edema. A new model for inflammation? Braz J Med Biol Res 20: 243-249., Hopkins 2003Hopkins SJ. 2003. The pathophysiological role of cytokines. Int J Legal Med 5: 45-57.). A similar reduction was observed in Evan's blue concentration in the pleural exudate, where the EEA promoted a reduction up to 50%, suggesting a reduction of protein extravasation to pleural cavity (Saleh et al. 1997Saleh TSF, Calixto JB and Medeiros YS. 1997. Proinflammatory effects induced by bradykinin in a murine model of pleurisy. Eur J Pharmacol 331: 43-52., Vianna and Calixto 1998Vianna RMJ and Calixto JB. 1998. Characterization of the receptor and the mechanisms underlying the inflammatory response induced by des-Arg9-bk in mouse pleusisy. Br J Pharmacol 123: 281-291.).

The croton oil causes leukocyte migration, increases the vascular permeability and the plasma exudation (Lapa 2003, Swingle et al. 1981Swingle KF, Reiter MJ and Schwartzmiller DH. 1981. Comparison of croton oil and cantharidin induced inflammations of the mouse ear and their modification by topically applied drugs. Arch Int Pharmacodyn Ther 254: 168-176.). The anti-edematogenic effect observed in this method suggests an anti-inflammatory action. Nevertheless, this model does not clearly show in which stage of the inflammatory process EEA acts.

The carrageenan-induced paw edema is a model of acute inflammation which involves a gradual and complex response (Winter et al. 1962Winter CA, Risley EA and Nuss GW. 1962. Carrageenin-induced edema in hind paw of the rat as an assay for antiinflamatory drugs. Proc Sot Exp Biol Med 111: 544-547.). The edema evolution is marked by the release of various inflammatory mediators such as histamine, bradykinin, serotonin and prostaglandins. These mediators are released at different times. In the first two hours, histamine and serotonin are the primary mediators; in the third hour, prostaglandins are predominant in the acute edema, while the complement system operates throughout the process (Di Rosa et al. 1971). In this test EEA reduced the edema in the first two hours.

Similar results were observed with extracts of leaf and stem bark of Lafoensia pacari, a Cerrado's species. These extracts showed antinociceptive activity in writhing test. The two phases of the formalin test reduced the ear edema and the cell migration, suggesting an analgesic and anti-inflammatory effect (Nascimento et al. 2011Nascimento MVM, Galdino PM, Florentino IF, Sampaio BL, Vanderlinde FA, Paula JR and Costa EA. 2011. Antinociceptive effect of Lafoensia pacari A. St.-Hil. Independent of anti-inflamatory of ellagic acid. J Nat Med 65: 448-454., Guimarães et al. 2010Guimarães HA, Nascimento MVM, Tavares A, Galdino PM, Paula JR and Costa EA. 2010. Effects of ethanolic extract of leaves of Lafoensia pacari A. St.-Hil., Lythraceae (pacari), in pain and inflammation models. Rev Bras Farmacogn 20(3): 328-333.). Nascimento et al. (2011)Nascimento MVM, Galdino PM, Florentino IF, Sampaio BL, Vanderlinde FA, Paula JR and Costa EA. 2011. Antinociceptive effect of Lafoensia pacari A. St.-Hil. Independent of anti-inflamatory of ellagic acid. J Nat Med 65: 448-454. showed that this analgesic activity may be independent of anti-inflammatory action of ellagic acid and that this effect is not blocked by naloxone.

The Spiranthera odoratissima, other Cerrado's specie popularly kwon by manacá, has only anti-inflammatory activity by reducing the writhing test, the second phase of formalin test, the ear edema, the second and third hours of paw edema, leukocyte migration, protein extravasation and inhibition of inflammation mediators such as phospholipase A2 and TNF-α, without analgesic effect in the first phase of the formalin and hot plate tests (Barbosa et al. 2012Barbosa DBM, Nascimento MVM, Lino RC, Magalhães MR, Florentino IF, Honório TCD, Galdino PM, Bara MTF, Paula JR and Costa EA. 2012. Mechanism involved in the anti-inflammatory effect of Spiranthera odoratissima (Manacá). Rev Bras Farmacogn IN PRESS, DOI: 10.1590/S0102-695X2011005000154.
https://doi.org/10.1590/S0102-695X201100...
, Nascimento et al. 2012Nascimento MVM, Galdino PM, Florentino IF, Brito AF, Paula JR, Silva RN and Costa EA. 2012. Anti-inflammatory effect of Spiranthera odoratissima A. St.-Hil. leaves involves reduction of TNF-α. Nat Prod Res IN PRESS.).

The inhibition in the edema caused by EEA in the first two hours suggests that the extract interferes with the action or release of serotonin or histamine, because these mediators are predominant in the initial phase of carrageenan-induced edema (Santos and Rao 2000Santos FA and Rao VSN. 2000. Antiinflammatory and antinociceptive effects of 1,8- cineole a terpenoid oxide present in many plant essential oils. Phytother Res 14: 240-244.). The effect observed with EEA in the dextran-induced edema model corroborates with this possibility. The dextran is a phlogistic agent known to induce edema mediated by 5-hydroxytryptamine and histamine (Lo et al. 1982Lo TN, Almeida AP and Beaven MA. 1982. Dextran and carrageenan evoke different infl amatory response in rat with respect to composition of infiltrates and effect of indomethacin. J Pharmacol Exp Ther 221: 261-267., Katz et al. 1984Katz LB, Theobald HD and Bookstaff RC. 1984. Characterization of the enhanced paw edema response to carrageenan and dextran in 2,3,7,8,- tetrachlorodibenzo-p-dioxin-treated rats. J Pharmacol Exp Ther 230: 670-677.).

Histamine is a vasoactive amine, which is among the preformed mediators released during the inflammatory process (Kumar et al. 2005Kumar V, Abbas AK and Fausto N. 2005. Robbins and Cotran. Patologia – Bases patológicas das doenças. 7a ed., Rio de Janeiro: Elsevier, p. 49-79.). This amine causes vasodilation and increases the vascular permeability through the action over specific receptors (H1 and H2), together with other inflammatory mediators (Sherwood and Toliver-Kinsky 2004Sherwood ER and Toliver-Kinsky T. 2004. Mechanisms of the inflammatory response. Best Pract Res Clin Anaesthesiol 18: 385-405.).

In this regard, serotonin (5-hydroxtryptamine [5-HT]) has long been associated with pain processing and modulation (Eide and Hole 1993Eide PK and Hole K. 1993. The role of 5-hydroxytryptamine (5-HT) receptor subtypes and plasticity in the 5-HT systems in the regulation of nociceptive sensitivity. Cephalalgia 13: 75-85.). Some studies have shown a spinal analgesic action of 5-HT released from brainstem structures (Yaksh and Wilson 1979Yaksh TL and Wilson PR. 1979. Spinal serotonin terminal system mediates antinociception. J Pharmacol Exp Ther 208: 446-453.). However, the peripheral action of serotonin is different from its central actions. Serotonin is considered an inflammatory mediator in the periphery, being released from platelets and mast cells after tissue injury (Dray 1995Dray A. 1995. Inflammatory mediators of pain. Br J Anaesth 75: 125-131.).

Moreover, our results with cyproheptadine pretreatment in the edema induced by dextran suggest a blocker action on both histaminergic H1 and serotonergic 5HT2 receptors (Rang et al. 2007Rang HP, Dale MM, Ritter JM and Moore PK. 2007. Farmacologia, 6a ed., Rio de Janeiro: Elsevier, p. 219.).

CONCLUSIONS

Results showed that the ethanolic extract (EEA) from acariçoba (Hydrocotyle umbellata) presents analgesic and anti-inflammatory activity in different experimental models, suggesting an anti-migration and anti-edematous action that can be due to the blockade or inhibition in the release of histamine or serotonin.

The authors declare that there are no conflicts of interest.

The authors are grateful to Dra. Ekaterina A. F. B. Rivera and Jackson Nascimento de Lima for technical assistance. This study was financially supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação de Apoio à Pesquisa (FUNAPE/UFG), Fundação de Amparo à Pesquisa do Estado de Goiás (FAPEG) e Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq).

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Publication Dates

  • Publication in this collection
    Sept 2013

History

  • Received
    20 Sept 2011
  • Accepted
    16 Apr 2012
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